A path is described using the concept of a current point. In
an analogy with drawing on paper, the current point can be
thought of as the location of the pen. The position of the pen
can be changed, and the outline of a shape (open or closed) can
be traced by dragging the pen in either straight lines or
curves.

Paths represent the geometry of the outline of an object,
defined in terms of moveto (set a new current point),
bearing (set a new orientation), lineto
(draw a straight line), curveto (draw
a curve using a cubic Bézier), arc (elliptical
or circular arc) and closepath (close the current
shape by drawing a line to the last moveto) commands.
Compound paths (i.e., a path with multiple subpaths) are
possible to allow effects such as "donut holes" in objects.

Path data animation is only possible when each path data
specification within an animation specification has exactly
the same list of path data commands as the ‘d’ attribute. If an animation is
specified and the list of path data commands is not the
same, then the animation specification is in error (see
Error Processing).
The animation engine interpolates each parameter to each
path data command separately based on the attributes to the
given animation element. Flags and booleans are
interpolated as fractions between zero and one, with any
non-zero value considered to be a value of one/true.

The Value in the table above should be a link to a datatype for path data.

The author's computation of the total length of the
path, in user units. This value is used to calibrate the
user agent's own distance-along-a-path
calculations with that of the author. The user agent will
scale all distance-along-a-path computations by the ratio
of ‘pathLength’ to the user
agent's own computed value for total path length. ‘pathLength’ potentially affects
calculations for text on a path,
motion animation and
various stroke operations.

8.3.1. General information about path data

A path is defined by including a ‘path’
element which contains a d="(path data)"
attribute, where the ‘d’ attribute contains the
moveto, bearing, lineto, curveto (both cubic and
quadratic Béziers), arc and closepath
instructions.

Example triangle01
specifies a path in the shape of a triangle. (The
M indicates a moveto, the
Ls indicate linetos, and the
z indicates a closepath).

Path data can contain newline characters and thus can be
broken up into multiple lines to improve readability. Because
of line length limitations with certain related tools, it is
recommended that SVG generators split long path data strings
across multiple lines, with each line not exceeding 255
characters. Also note that newline characters are only allowed
at certain places within path data.

The path data is defined to allow newline
characters, but it should be noted that newlines inside
attributes in markup will be normalized to space characters
while parsing. If you wanted to, you could write

<path d="M 100,100&#10;L 200,150"/>

but it's not likely that you'd want to.

Are there tools that have line limits nowadays?
Do we still need to recommend generators to split up path data
at 255 characters?

The sentence about newline characters being
allowed only at certain places makes it sound like these places
are different from where white space more generally is allowed,
but that's not the case.

The syntax of path data is concise in order to allow for
minimal file size and efficient downloads, since many SVG files
will be dominated by their path data. Some of the ways that SVG
attempts to minimize the size of path data are as follows:

All instructions are expressed as one character (e.g., a
moveto is expressed as an M).

Superfluous white space and separators such as commas can
be eliminated (e.g., "M 100 100 L 200 200" contains
unnecessary spaces and could be expressed more compactly as
"M100 100L200 200").

The command letter can be eliminated on subsequent
commands if the same command is used multiple times in a row
(e.g., you can drop the second "L" in "M 100 200 L 200 100 L
-100 -200" and use "M 100 200 L 200 100 -100 -200"
instead).

For most commands there are absolute and relative
versions available (uppercase means absolute coordinates,
lowercase means relative coordinates).

Alternate forms of lineto are available to
optimize the special cases of horizontal and vertical lines
(absolute and relative).

Alternate forms of curve are available to
optimize the special cases where some of the control points
on the current segment can be determined automatically from
the control points on the previous segment.

The path data syntax is a prefix notation (i.e., commands
followed by parameters). The only allowable decimal point is a
Unicode
U+0046 FULL STOP (".") character (also referred to in Unicode as
PERIOD, dot and decimal point) and no other delimiter
characters are allowed [UNICODE].
(For example, the following is an
invalid numeric value in a path data stream: "13,000.56".
Instead, say: "13000.56".)

For the relative versions of the commands, all coordinate
values are relative to the current point at the start of the
command.

Relative path commands are also influenced by the
current bearing, which is an angle set by the bearing
commands. This allows for paths to be specified using a
style of "turtle graphics", where straight line and curved
path segments are placed with their starting point at a
tangent (or at some other angle) to the current bearing.

In the tables below, the following notation is used to
describe the syntax of a given path command:

(): grouping of parameters

+: 1 or more of the given parameter(s) is required

In the description of the path commands, cpx and
cpy represent the coordinates of the current point,
and cb represents the current bearing.

The following sections list the commands.

8.3.2. The "moveto" commands

The "moveto" commands (M or
m) establish a new current point. The effect
is as if the "pen" were lifted and moved to a new location. A
path data segment (if there is one) must begin with a "moveto"
command. Subsequent "moveto" commands (i.e., when the "moveto"
is not the first command) represent the start of a new
subpath:

Command

Name

Parameters

Description

M (absolute)m (relative)

moveto

(x y)+

Start a new sub-path at the given (x,y) coordinates.
M (uppercase) indicates that absolute
coordinates will follow; m (lowercase)
indicates that relative coordinates will follow. If a moveto is
followed by multiple pairs of coordinates, the subsequent pairs
are treated as implicit lineto commands. Hence, implicit lineto
commands will be relative if the moveto is relative, and
absolute if the moveto is absolute. If a relative moveto
(m) appears as the first element of the path,
then it is treated as a pair of absolute coordinates. In this
case, subsequent pairs of coordinates are treated as relative
even though the initial moveto is interpreted as an absolute moveto.

8.3.3. The "closepath" command

The "closepath" (Z or z)
ends the current subpath and causes an automatic straight line
to be drawn from the current point to the initial point of the
current subpath. If a "closepath" is followed immediately by a
"moveto", then the "moveto" identifies the start point of the
next subpath. If a "closepath" is followed immediately by any
other command, then the next subpath starts at the same initial
point as the current subpath.

When a subpath ends in a "closepath," it differs in behavior
from what happens when "manually" closing a subpath via a
"lineto" command in how ‘stroke-linejoin’
and ‘stroke-linecap’ are implemented. With "closepath", the end of the final segment
of the subpath is "joined" with the start of the initial
segment of the subpath using the current value of ‘stroke-linejoin’.
If you instead "manually" close the subpath via a "lineto"
command, the start of the first segment and the end of the last
segment are not joined but instead are each capped using the
current value of ‘stroke-linecap’.
At the end of the command, the new current point is set to the
initial point of the current subpath.

The current bearing does not affect a z command.

Command

Name

Parameters

Description

Z orz

closepath

(none)

Close the current subpath by drawing a straight line from the
current point to current subpath's initial point. Since the
Z and z
commands take no parameters, they have an identical effect.

8.3.4. The "lineto" commands

The various "lineto" commands draw straight lines from the
current point to a new point:

Command

Name

Parameters

Description

L (absolute)l (relative)

lineto

(x y)+

Draw a line from the current point to the given (x,y)
coordinate which becomes the new current point.
L (uppercase) indicates that absolute
coordinates will follow; l (lowercase)
indicates that relative coordinates will follow. A number
of coordinates pairs may be specified to draw a polyline.
At the end of the command, the new current point is set to
the final set of coordinates provided.

H (absolute)h (relative)

horizontal lineto

x+

Draws a horizontal line from the current point.
H (uppercase) indicates
that absolute coordinates will follow; h
(lowercase) indicates that relative coordinates will
follow. Multiple x values can be provided (although usually
this doesn't make sense). An H or h
command is equivalent to an L or l
command with 0 specified for the y coordinate.
At the end of the command, the new current point is
taken from the final coordinate value.

V (absolute)v (relative)

vertical lineto

y+

Draws a vertical line from the current point.
V (uppercase) indicates that
absolute coordinates will follow; v
(lowercase) indicates that relative coordinates will
follow. Multiple y values can be provided (although usually
this doesn't make sense). A V or v
command is equivalent to an L or l
command with 0 specified for the x coordinate.
At the end of the command, the new current point is
taken from the final coordinate value.

When a relative l command is used, the
end point of the line is (cpx + x cos cb
+ y sin cb, cpy +
x sin cb + y cos cb).

When a relative h command is used,
the end point of the line is (cpx + x cos cb,
cpy + x sin cb). This means
that an h command with a positive x
value draws a line in the direction of the current bearing. When
the current bearing is 0, this is a horizontal line in the direction
of the positive x-axis.

When there is a non-zero bearing, a mnemonic for the h
command could be "head this distance at the current bearing",
rather than "draw a horizontal line".

When a relative v command is used,
the end point of the line is (cpx + y sin cb,
cpy + y cos cb).

8.3.5. The curve commands

These three groups of commands draw curves:

Cubic
Bézier commands (C,
c, S and
s). A cubic Bézier segment is defined
by a start point, an end point, and two control points.

Quadratic
Bézier commands (Q,
q, T and
t). A quadratic Bézier segment is
defined by a start point, an end point, and one control
point.

8.3.6. The cubic Bézier curve commands

The cubic Bézier commands are as follows:

Command

Name

Parameters

Description

C (absolute)c (relative)

curveto

(x1 y1 x2 y2 x y)+

Draws a cubic Bézier curve from the current
point to (x,y) using (x1,y1) as the control point at the
beginning of the curve and (x2,y2) as the control point at
the end of the curve. C (uppercase)
indicates that absolute coordinates will follow;
c (lowercase) indicates that relative
coordinates will follow. Multiple sets of coordinates may
be specified to draw a polybézier. At the end of the
command, the new current point becomes the final (x,y)
coordinate pair used in the polybézier.

S (absolute)s (relative)

shorthand/smooth curveto

(x2 y2 x y)+

Draws a cubic Bézier curve from the current
point to (x,y). The first control point is assumed to be
the reflection of the second control point on the previous
command relative to the current point. (If there is no
previous command or if the previous command was not an C,
c, S or s, assume the first control point is coincident
with the current point.) (x2,y2) is the second control
point (i.e., the control point at the end of the curve).
S (uppercase) indicates that absolute
coordinates will follow; s (lowercase)
indicates that relative coordinates will follow. Multiple
sets of coordinates may be specified to draw a
polybézier. At the end of the command, the new
current point becomes the final (x,y) coordinate pair used
in the polybézier.

When a relative c or s
command is used, each of the relative coordinate pairs
is computed as for those in an m command.
For example, the final control point of the curve of
both commands is (cpx + x cos cb
+ y sin cb, cpy +
x sin cb + y cos cb).

Example cubic01 shows some
simple uses of cubic Bézier commands within a path. The
example uses an internal CSS style sheet to assign styling
properties. Note that the control point for the "S" command is
computed automatically as the reflection of the control point
for the previous "C" command relative to the start point of the
"S" command.

The following picture shows some how cubic Bézier
curves change their shape depending on the position of the
control points. The first five examples illustrate a single
cubic Bézier path segment. The example at the lower
right shows a "C" command followed by an "S" command.

8.3.7. The quadratic Bézier curve commands

The quadratic Bézier commands are as follows:

Command

Name

Parameters

Description

Q (absolute)q (relative)

quadratic Bézier curveto

(x1 y1 x y)+

Draws a quadratic Bézier curve from the current
point to (x,y) using (x1,y1) as the control point.
Q (uppercase) indicates that absolute
coordinates will follow; q (lowercase)
indicates that relative coordinates will follow. Multiple
sets of coordinates may be specified to draw a
polybézier. At the end of the command, the new
current point becomes the final (x,y) coordinate pair used
in the polybézier.

T (absolute)t (relative)

Shorthand/smooth quadratic Bézier curveto

(x y)+

Draws a quadratic Bézier curve from the current
point to (x,y). The control point is assumed to be the
reflection of the control point on the previous command
relative to the current point. (If there is no previous
command or if the previous command was not a Q, q, T or t,
assume the control point is coincident with the current
point.) T (uppercase) indicates that
absolute coordinates will follow; t
(lowercase) indicates that relative coordinates will
follow. At the end of the command, the new current point
becomes the final (x,y) coordinate pair used in the
polybézier.

When a relative q or t
command is used, each of the relative coordinate pairs
is computed as for those in an m command.
For example, the final control point of the curve of
both commands is (cpx + x cos cb
+ y sin cb, cpy +
x sin cb + y cos cb).

Example quad01 shows some
simple uses of quadratic Bézier commands within a path.
Note that the control point for the "T" command is computed
automatically as the reflection of the control point for the
previous "Q" command relative to the start point of the "T"
command.

Draws an elliptical arc from the current point to
(x, y). The size and
orientation of the ellipse are defined by two radii
(rx, ry) and an
x-axis-rotation, which indicates how the
ellipse as a whole is rotated relative to the current
coordinate system. The center (cx,
cy) of the ellipse is calculated
automatically to satisfy the constraints imposed by the
other parameters. large-arc-flag and
sweep-flag contribute to the automatic
calculations and help determine how the arc is drawn.

When a relative a command is used, the end point
of the arc is (cpx + x cos cb
+ y sin cb, cpy +
x sin cb + y cos cb).
The effective value of the x-axis-rotation parameter is
also affected by the current bearing: it is computed as
x-axis-rotation + cb.

The elliptical arc command draws a section of an ellipse
which meets the following constraints:

the arc starts at the current point

the arc ends at point (x,
y)

the ellipse has the two radii (rx,
ry)

the x-axis of the ellipse is rotated by
x-axis-rotation relative to the x-axis of
the current coordinate system.

For most situations, there are actually four different arcs
(two different ellipses, each with two different arc sweeps)
that satisfy these constraints. large-arc-flag
and sweep-flag indicate which one of the four
arcs are drawn, as follows:

Of the four candidate arc sweeps, two will represent an
arc sweep of greater than or equal to 180 degrees (the
"large-arc"), and two will represent an arc sweep of less
than or equal to 180 degrees (the "small-arc"). If
large-arc-flag is '1', then one of the two
larger arc sweeps will be chosen; otherwise, if
large-arc-flag is '0', one of the smaller
arc sweeps will be chosen,

If sweep-flag is '1', then the arc will
be drawn in a "positive-angle" direction (i.e., the ellipse
formula x=cx+rx*cos(theta)
and y=cy+ry*sin(theta) is
evaluated such that theta starts at an angle corresponding to
the current point and increases positively until the arc
reaches (x,y)). A value of 0 causes the arc to be drawn in a
"negative-angle" direction (i.e., theta starts at an angle
value corresponding to the current point and decreases until
the arc reaches (x,y)).

The following illustrates the four combinations of
large-arc-flag and sweep-flag
and the four different arcs that will be drawn based on the
values of these flags. For each case, the following path data
command was used:

8.3.9. The bearing commands

The bearing commands (B or b)
set the current bearing, which influences the orientation of
subsequent relative path commands:

Command

Name

Parameters

Description

B (absolute)b (relative)

bearing

angle+

Sets the current bearing. The parameter is an angle
in degrees, where 0 indicates the direction of the positive
x-axis. B (uppercase) sets
the current bearing to the specified angle; b
(lowercase) sets the current bearing to be the angle of the
tangent at the end of the preceding path command plus the
specified angle. The current point is unaffected.
Although multiple parameters may be specified, this usually
will not be useful, as they could be combined into a single
angle value.

At the beginning of a path, the current bearing is 0, which
points in the direction of the positive x-axis. The current
bearing remains unchanged until a B or
b command is encountered. Since the relative
b command sets the current bearing relative
to the tangent at the end of the preceding path command,
it is possible to set the bearing to that tangent by using
"b 0".

The example below shows how bearing commands can be used
to draw a regular pentagon.

The processing of the BNF must consume as much of a given
BNF production as possible, stopping at the point when a
character is encountered which no longer satisfies the
production. Thus, in the string "M 100-200", the first
coordinate for the "moveto" consumes the characters "100" and
stops upon encountering the minus sign because the minus sign
cannot follow a digit in the production of a "coordinate". The
result is that the first coordinate will be "100" and the
second coordinate will be "-200".

Similarly, for the string "M 0.6.5", the first coordinate of
the "moveto" consumes the characters "0.6" and stops upon
encountering the second decimal point because the production of
a "coordinate" only allows one decimal point. The result is
that the first coordinate will be "0.6" and the second
coordinate will be ".5".

Note that the BNF allows the path ‘d’ attribute to be empty. This is not
an error, instead it disables rendering of the path.

Exact mathematics exist for computing distance along a path,
but the formulas are highly complex and require substantial
computation. It is recommended that authoring products and user
agents employ algorithms that produce as precise results as
possible; however, to accommodate implementation differences
and to help distance calculations produce results that
approximate author intent, the ‘pathLength’ attribute can be used
to provide the author's computation of the total length of the
path so that the user agent can scale distance-along-a-path
computations by the ratio of ‘pathLength’ to the user agent's own
computed value for total path length.

A "moveto" or "bearing" operation within a ‘path’ element is defined to have
zero length. Only the various "lineto", "curveto" and "arcto"
commands contribute to path length calculations.

8.5. DOM interfaces

8.5.1. Interface SVGPathSeg

The SVGPathSeg interface is a base interface that corresponds to a
single command within a path data specification.

Clears all existing current items from the list and re-initializes the
list to hold the single item specified by the parameter. If the inserted
item is already in a list, it is removed from its previous list before
it is inserted into this list. The inserted item is the item itself and
not a copy.

Inserts a new item into the list at the specified position. The first
item is number 0. If newItem is already in a list, it is
removed from its previous list before it is inserted into this list.
The inserted item is the item itself and not a copy. If the item is
already in this list, note that the index of the item to insert
before is before the removal of the item.

The index of the item before which the new item is to be
inserted. The first item is number 0. If the index is equal to 0,
then the new item is inserted at the front of the list. If the index
is greater than or equal to numberOfItems, then the new item is
appended to the end of the list.

Replaces an existing item in the list with a new item. If
newItem is already in a list, it is removed from its
previous list before it is inserted into this list. The inserted item
is the item itself and not a copy. If the item is already in this
list, note that the index of the item to replace is before
the removal of the item.

Inserts a new item at the end of the list. If newItem is
already in a list, it is removed from its previous list before it is
inserted into this list. The inserted item is the item itself and
not a copy.

8.5.22. Interface SVGAnimatedPathData

The SVGAnimatedPathData interface supports elements which have a ‘d’
attribute which holds SVG path data, and supports the ability to animate
that attribute.

The SVGAnimatedPathData interface provides two lists to access and
modify the base (i.e., static) contents of the ‘d’ attribute:

DOM attribute pathSegList provides access to the static/base
contents of the ‘d’ attribute in a form which matches one-for-one
with SVG's syntax.

DOM attribute normalizedPathSegList provides normalized access
to the static/base contents of the ‘d’ attribute where all path
data commands are expressed in terms of the following subset of
SVGPathSeg types:
SVG_PATHSEG_MOVETO_ABS (M),
SVG_PATHSEG_LINETO_ABS (L),
SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and
SVG_PATHSEG_CLOSEPATH (z).

and two lists to access the current animated values of the ‘d’
attribute:

DOM attribute animatedPathSegList provides access to the current
animated contents of the ‘d’ attribute in a form which matches
one-for-one with SVG's syntax.

DOM attribute animatedNormalizedPathSegList provides
normalized access to the current animated contents of the ‘d’
attribute where all path data commands are expressed in terms of the
following subset of SVGPathSeg types:
SVG_PATHSEG_MOVETO_ABS (M),
SVG_PATHSEG_LINETO_ABS (L),
SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and
SVG_PATHSEG_CLOSEPATH (z).

Each of the two lists are always kept synchronized. Modifications to one
list will immediately cause the corresponding list to be modified.
Modifications to normalizedPathSegList might cause entries in
pathSegList to be broken into a set of normalized path segments.

Additionally, the ‘d’ attribute on the ‘path’ element
accessed via the XML DOM (e.g., using the getAttribute()
method call) will reflect any changes made to pathSegList or
normalizedPathSegList.

Provides access to the base (i.e., static) contents of the ‘d’
attribute in a form which matches one-for-one with SVG's syntax.
Thus, if the ‘d’ attribute has an "absolute moveto (M)" and an
"absolute arcto (A)" command, then pathSegList will have two
entries: a SVG_PATHSEG_MOVETO_ABS and a SVG_PATHSEG_ARC_ABS.

Provides access to the base (i.e., static) contents of the
‘d’ attribute in a form where all path data commands are
expressed in terms of the following subset of SVGPathSeg
types: SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L),
SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH
(z). Thus, if the ‘d’ attribute has an "absolute moveto (M)"
and an "absolute arcto (A)" command, then pathSegList will
have one SVG_PATHSEG_MOVETO_ABS entry followed by a series of
SVG_PATHSEG_LINETO_ABS entries which approximate the arc. This
alternate representation is available to provide a simpler
interface to developers who would benefit from a more limited set
of commands.

Provides access to the current animated contents of the ‘d’
attribute in a form which matches one-for-one with SVG's syntax.
If the given attribute or property is being animated, contains
the current animated value of the attribute or property, and both
the object itself and its contents are read only. If the given
attribute or property is not currently being animated, contains
the same value as pathSegList.

Provides access to the current animated contents of the
‘d’ attribute in a form where all path data commands
are expressed in terms of the following subset of SVGPathSeg
types: SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L),
SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH (z).
If the given attribute or property is being animated, contains
the current animated value of the attribute or property, and both
the object itself and its contents are read only. If the given
attribute or property is not currently being animated, contains
the same value as normalizedPathSegList.